As one method for performing 3rd generation cellular mobile communication, a communication standard for the W-CDMA (Wideband Code Division Multiple Access) scheme has been standardized by 3GPP (3rd Generation Partnership Project) which is an international standardization project. Mobile telephone services based on this standard are starting up one after another in various countries. In 3GPP examinations have been undertaken into communication technologies known as EUTRA (Evolved Universal Terrestrial Radio Access) and EUTRAN (Evolved Universal Terrestrial Radio Access Network) as new standards for this type of 3rd generation radio system. In addition, the HSDPA (High Speed Downlink Packet Access) system, which makes it possible for high speed packet communication in a W-CDMA system downlink to be performed, has also been standardized.
A simple summary will now be given of the HSDPA system and of EUTRA.
In the HSDPA system, downlink physical channels include HS-PDSCH (High Speed Physical Downlink Shared Channel) and HS-DSCH-related Shared Control Channel HS-SCCH.
The high speed physical downlink shared channel HS-PDSCH is a shared channel which is shared on the downlink by a plurality of mobile stations, and is used to transmit packet data addressed to the respective mobile stations. The HS-DSCH (High Speed Downlink Shared Channel) system is included in this HS-PDSCH as a transport channel.
The HS-DSCH-related Shared Control Channel HS-SCCH is a shared channel which is shared on the downlink by a plurality of mobile stations, and is used to transmit information about the modulation scheme and spreading code which is required information in order for each mobile station to demodulate the High Speed Physical Downlink Shared Channel HS-PDSCH, information required for error correction decoding, and information required for a HARQ (Hybrid Automatic Repeat reQuest).
Uplink physical channels in an HSDPA system include the HS-DPCCH (Dedicated Physical Control Channel for HS-DSCH).
The High Speed Dedicated Physical Control Channel HS-DPCCH for HS-DSCH is a control channel which the respective mobile stations use individually on the uplink, and is used to transmit downlink channel transmission path quality information (Channel Quality Indicators; CQI) and ACK/NACK (Acknowledgement/Negative Acknowledgement) signals which form reception confirmation information corresponding to HARQ signals.
Next, in EUTRA, an OFDM (Orthogonal Frequency Division Multiplexing) system is used for the downlink, and Adaptive Modulation and Coding Scheme (AMCS) technology which is based on adaptive radio link control such as channel coding and the like is used in this OFDM system. AMCS is a communication system which, in accordance with the transmission path situations of the respective mobile stations, switches between a variety of radio transmission parameters such as the error correction system, the error correction code rate, the number of data modulation multi-values, the code spreading rate of the time and frequency axes, and the multi-code multiplex number and the like in order to perform high speed packet data transmission efficiently. For example, in data modulation, by switching to more efficient multi-valued modulation such as switching from QPSK (Quadri-Phase Shift keying) to 8PSK (8 Phase Shift Keying) or 16QAM (16 Quadrature Amplitude Modulation) as the situation of the transmission path improves, it is possible to increase the maximum throughput of a communication system.
Moreover, two channel arrangement systems in an OFDM system have been proposed, namely, a Spread-OFDM system and a Non Spread-OFDM system. In a Spread-OFDM system, a physical control channel and a physical data channel are multiplexed on the same frequency band by means of spreading code multiplexing. In a Non Spread-OFDM system, a physical control channel and a physical data channel are multiplexed in time and frequency by employing TDM (Time Division Multiplexing), FDM (Frequency Division Multiplexing), or a combination of TDM and FDM.
In EUTRA, radio frames for downlinks based on an OFDM system are divided in a frequency direction and a time direction, and the data for each mobile station is mapped onto each of these divided blocks. By using mobile station identification information which identifies the respective mobile stations in order to perform this mapping, allocation information showing the allocation of mobile stations to each block is transmitted from the base station.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2001-237803
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2004-297756